Financial Instruments (Schedule Of Derivatives And Hedged Items In Fair Value Hedging Relationships) (Details) $ in Thousands	12 Months Ended
	Sep. 30, 2017 USD ($)
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) on Derivative Recognized in the Consolidated Statement of Income	$ 2,119
Amount of Gain or (Loss) on Hedged Item Recognized in the Consolidated Statement of Income	(2,119)
Operating Revenues [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) on Derivative Recognized in the Consolidated Statement of Income	1,655
Amount of Gain or (Loss) on Hedged Item Recognized in the Consolidated Statement of Income	(1,655)
Purchased Gas [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) on Derivative Recognized in the Consolidated Statement of Income	464
Amount of Gain or (Loss) on Hedged Item Recognized in the Consolidated Statement of Income	$ (464)